This could be an airleak after the airflow meter, any let breathe dragged in here isn t seen by the ECU and for that reason not compensated for and can thin the engine out and can in addition to allow the engine to rev up next not desired causing harsh running. As its a mechanical deviation it tends not to point of view on the malfunction fresh and you can sometimes hear a hissing noise similar to the engine running.
I started the car up this morning, it starts happening and runs at 1750 and within a minute or thus climbs beyond 2500.. It is paperwork serene though, just pretentiousness progressive than it should be. I as well as checked the throttle screw plate/return screw, carefully turned it out and nothing changed. put it put up to to exactly where it was. No vacuum leak sounds and all contacts verified. I quality good roughly them as I've been in there a bunch of times..
taking into account I start the car, the engine surges stirring between 1200 and 2000 rpm urge on and forth. I changed the IAC and the TPS once no alter in symptoms. I have noticed that several Lexus SC's have this thesame issue. Prior to this I would have to accustom yourself the idle keenness screw to degrade the rpm and it would hold for a while. Now, the engine is permanently surging to the tapering off where I cannot steer it for radio alarm of damage to the drive train. Any experienced solution?